FIG. 1 illustrates a prior art gate drive circuit for a switching power supply. The circuit of FIG. 1 includes two transistors Q1 and Q2 connected to a switch node SW and arranged to alternately switch an inductor between two different power supply terminals PS and GND. This type of switch arrangement is commonly used in switching power supplies such as a synchronous buck converter. Transistors Q1 and Q2 are controlled by input signals IN1 and IN2 which drive the gates of Q1 and Q2 through drive circuits 10 and 12, respectively.
Drive circuit 12 can receive its power from the positive power supply terminal PS because the source of Q2 is referenced to the power supply ground terminal GND. However, the source of Q1 is referenced to the switch terminal SW which is at nearly the same voltage as PS when the gate of Q1 must be driven with a significantly higher voltage than PS. Therefore, the circuit of FIG. 1 includes a boost circuit 14 to generate a boosted power supply BST which is used to operate the drive circuit 10 for Q1. Boost circuit 14 includes a diode DB and capacitor CB connected in a charge pump arrangement.
The circuit of FIG. 1 also includes an RC snubber circuit 16 which dampens voltage spikes at the switch terminal SW caused by parasitic inductances in the transistors, the PC board on which they may be mounted, as well as the main inductor for the switching power supply.